Heat capacity evidence for the suppression of skyrmions at large zeeman energy

Measurements on a multilayer two-dimensional electron system (2DES) near Landau-level filling ν = 1 reveal the disappearance of the nuclear spin contribution to the heat capacity as the ratio^∼g between the Zeeman and Coulomb energies exceeds a critical value^∼g_c≈ 0.04. This disappearance suggests the vanishing of the Skyrmion-mediated coupling between the lattice and the nuclear spins as the spin excitations of the 2DES make a transition from Skyrmions to single spin flips above^∼g_c. Our experimental^∼g_cis smaller than the calculated^∼g_c= 0.054 for an ideal 2DES. We discuss possible origins of this discrepancy.